Abstract:
Magnetorheological (MR) fluid dampers have been an attractive candidate in structural control because of
its great potential in the mitigation of dynamic effects caused by seismic excitations in civil engineering
structures. The MR damper features a passive mode that is fault-safe under disastrous situations such as
earthquakes. It also requires only a very small amount of driving power as compared to the active mass
control devices. A major drawback of MR damper applications is, however, the nonlinear hysteresis
characteristics in the force/velocity relationship. Sliding mode control, well-recognised for its superproperty
of robustness to parametric uncertainties and un-modelled disturbances in control systems,
appears to be suitable for structural control using MR dampers. To overcome the difficulty in obtaining an
exact parameter set characterising the MR damper dynamics in a wide operating range, the effect of
uncertainties arisen from the damper parameters is to be handled by using a multi-level sliding mode
controller, proposed in this paper. Here, the control effort is quantised into a finite number of levels,
corresponding to lin appropriate set of the damper parameters. This approach avoids the need for
extensive parameter identification experiments, and also the unnecessary energy consumption usually
associated with the discontinuous control component. The effectiveness of the proposed controller is
demonstrated by simulations.
